The present invention relates generally to an impeller for a centrifugal pump, as well as to a centrifugal pump with such an impeller.
Impellers are applied in numerous types of centrifugal pumps. Impellers often have an extremely complex geometry which renders it difficult to manufacture them by way of injection molding. For this reason, it is necessary in many cases to manufacture two separate parts and to then join these together.
With impellers of plastic which are manufactured, for example ,of fiber-reinforced plastic materials such as polymer composite materials or plastic composite materials, the parts of the impellers are connected, for example, by way of ultrasound welding. Ultrasound welding, however, often causes asymmetries in the impellers. One of the main disadvantages with the use of ultrasound welding is the fact that problems with regard to the eccentricity of the impellers can often occur with ultrasound-welded impellers.
Ultrasound welding is known in the state of the art for connecting complex plastic parts. These parts are usually inserted in a sandwich-like manner between a fixed part and a further part which is connected to a transducer, in order to couple in an acoustic vibration.
The ultrasound produces a connection when the contact points between the parts begin the melt. Ultrasound welding causes local melting of the plastic due to the absorption of the vibration energy and thus deformations can occur at locations, which causes the mentioned asymmetries of the impeller.
With some impellers of the state of the art, the parts are connected amid the use of mechanical connection methods and laser welding, so that the impeller does not become asymmetrical. Mechanical connections are realized by way of one of the impeller parts obtaining groove-like structures. Such impellers, however, can likewise turn out to be asymmetrical due to inaccuracies of the groove-like structures.
Accordingly, an increased leakage flow can occur between the suction side and the pump housing of the impeller and this leads to a reduced efficiency of the pump, in which the impeller is inserted.